USTC realizes quantum-enhanced microwave ranging

On March 9, Nature Communications published research by Academician GUO Guangcan's team from the University of Science and Technology of China (USTC), which made significant progress in practical quantum sensing. The team, led by Prof. SUN Fangwen, used micro and nano quantum sensing with local enhancement of electromagnetic fields at deep sub-wavelengths to study the detection of microwave signals and wireless ranging, achieving a positioning accuracy of 10^-4 wavelengths.

Radar positioning technology based on microwave signal measurement is widely used in activities such as automatic driving, intelligent manufacturing, health monitoring, and geological exploration. In this study, the research group combined quantum sensing of solid-state systems with micro/nano resolution and deep subwavelength localization of electromagnetic fields to develop high-sensitivity microwave detection and high-precision microwave positioning technology.

The group designed a composite microwave antenna composed of diamond spin quantum sensors and metal nanostructures, which collects and converges microwave signals propagating in free space into nano-space. By probing the solid-state quantum probe state in the local domain, they measured the microwave signals. The method converted the detection of weak signals in free space into the detection of electromagnetic field and solid-state spin interactions at the nanoscale, improving the microwave signal measurement sensitivity of solid-state quantum sensors by 3-4 orders of magnitude.

To further utilize the high sensitivity microwave detection to achieve high-precision microwave localization, the research group built a microwave interferometry device based on the diamond quantum sensor, and obtained the phase of the reflected microwave signal and the position information of the object through the solid-state spin detection of the interference result between the reflected microwave signal and the reference signal of the object. Based on the coherent interaction between solid-state spin quantum probes and microwave photons multiple times, they achieved quantum-enhanced position measurement with an accuracy of 10 micrometers (about one ten-thousandth of the wavelength).

Compared with traditional radar systems, this quantum measurement method does not require active devices such as amplifiers at the detection end, reducing the impact of electronic noise and other factors on the measurement limit. Subsequent research will allow further improvement of radio localization accuracy, sampling rate, and other indicators based on solid-state spin quantum sensing, and the development of practical solid-state quantum radar localization technology that exceeds the performance level of existing radars.